The present invention relates to a ball valve comprising a valve case and a ball valve element disposed in the case and turnable for controlling the flow of fluid through the valve.
For controlling the flow rate of a fluid with a ball valve, the ball valve element within the case of the valve is usually turned by a lever through the valve stem to alter the direction of the flow channel extending through the ball valve element. Accordingly the lever must be operated very delicately for the fine adjustment of the flow rate. Such delicate manipulation of the lever is very cumbersome, while the flow is not always adjustable accurately by operating the lever.